In this article

Configure Trusted Roots and Disallowed Certificates

08/29/2017

19 minutes to read

In this article

Applies To: Windows 8.1, Windows Server 2012 R2

The Windows Server 2012 R2, Windows Server 2012, Windows 8.1, and Windows 8 operating systems include an automatic update mechanism that downloads certificate trust lists (CTLs) on a daily basis. In Windows Server 2012 R2 and Windows 8.1, additional capabilities are available to control how the CTLs are updated.

Important

Software updates are available for Windows Server 2012, Windows Server 2008 R2, Windows Server 2008, Windows 8, Windows 7, and Windows Vista. To provide the enhancements of the automatic update mechanism that are discussed in this document, apply the following updates:

Trusted root certificates are meant to be placed in the Trusted Root Certification Authorities certificate of the Windows operating systems. These certificates are trusted by the operating system and can be used by applications as a reference for which public key infrastructure (PKI) hierarchies and digital certificates that are trustworthy.

When you want to distribute trusted root certificates, the list of trusted root certificates is stored in a CTL. Client computers access the Windows Update site by using the automatic update mechanism to update this CTL.

Note

The list of trusted root certificates is called the trusted CTL.

Untrusted certificates are certificates that are publicly known to be fraudulent. Like the trusted CTL, the list of untrusted certificates is stored in a CTL. Client computers access the Windows Update site by using the automatic update mechanism to update this CTL.

Prior to Windows Server 2012 R2 and Windows 8.1 (or the installation of the software update, as previously discussed), the same registry setting controlled updates for trusted root certificates and untrusted certificates. An administrator could not selectively enable or disable one or the other. This resulting in the following challenges:

Although disabling automatic updates for trusted CTLs is recommended for administrators who manage their lists of trusted root certificates (in disconnected or connected environments), disabling automatic updates of untrusted CTLs is not recommended.

Because there was not a method for network administrators to view and extract only the trusted root certificates in a trusted CTL, managing a customized list of trusted certificates was difficult task.

Software update description

The following improved automatic update mechanisms for a disconnected environment are available in Windows Server 2012 R2 and Windows 8.1 or when the appropriate software update is installed:

Registry settings for storing CTLs New settings enable changing the location for uploading trusted or untrusted CTLs from the Windows Update site to a shared location in an organization. For more information, see the Registry settings modified section.

Synchronization options If the URL for the Windows Update site is moved to a local shared folder, the local shared folder must be synchronized with the Windows Update folder. This software update adds a set of options in the Certutil tool that administrators can use to enable synchronization. For more information, see the New Certutil Options section.

Tool to select trusted root certificates This software update introduces a tool for administrators who manage the set of trusted root certificates in their enterprise environment. Administrators can view and select the set of trusted root certificates, export them to a serialized certificate store, and distribute them by using Group Policy. For more information, see the New Certutil Options section in this document.

Independent configurability The automatic update mechanism for trusted and untrusted certificates are independently configurable. This enables administrators to use the automatic update mechanism to download only the untrusted CTLs and manage their own list of trusted CTLs. For more information, see the Registry settings modified section in this document.

Configuration options

In Windows Server 2012 R2 and Windows 8.1 (or by installing the previously mentioned software updates on supported operating systems), an administrator can configure a file or web server to download the following files by using the automatic update mechanism:

authrootstl.cab, which contains a non-Microsoft CTL

disallowedcertstl.cab, which contains a CTL with untrusted certificates

disallowedcert.sst, which contains a serialized certificate store, including untrusted certificates

Examine the set of root certificates in the Windows Root Certificate Program. This enables administrators to select a subset of certificates to distribute by using a Group Policy Object (GPO). This is configuration is described in the Use a subset of the trusted CTLs section of this document.

Important

All the steps shown in this document require that you use an account that is a member of the local Administrators group. For all Active Directory Domain Services (AD DS) configuration steps, you must use an account that is a member of the Domain Admins group or that has been delegated the necessary permissions.
The procedures in this document depend upon having at least one computer that is able to connect to the Internet to download CTLs from Microsoft. The computer requires HTTP (TCP port 80) access and name resolution (TCP and UDP port 53) ability to contact ctldl.windowsupdate.com. This computer can be a domain member or a member of a workgroup. Currently all the downloaded files require approximately 1.5 MB of space.
The settings described in this document are implemented by using GPOs. These settings are not automatically removed if the GPO is unlinked or removed from the AD DS domain. When implemented, these settings can be changed only by using a GPO or by modifying the registry of the affected computers.
The concepts discussed in this document are independent of Windows Server Update Services (WSUS).

Configure a file or web server to download the CTL files

To facilitate the distribution of trusted or untrusted certificates for a disconnected environment, you must first configure a file or web server to download the CTL files from the automatic update mechanism.

Tip

The configuration described in this section is not needed for environments where computers are able to connect to the Windows Update site directly. Computers that can connect to the Windows Update site are able to receive updated CTLs on a daily basis (if they are running Windows Server 2012, Windows 8, or the previously mentioned software updates are installed on supported operating systems). For more information, see document 2677070 in the Microsoft Knowledge Base.

To configure a server that has access to the Internet to retrieve the CTL files

Create a shared folder on a file or web server that is able to synchronize by using the automatic update mechanism and that you want to use to store the CTL files.

Tip

Before you begin, you may have to adjust the shared folder permissions and NTFS folder permissions to allow the appropriate account access, especially if you are using a scheduled task with a service account. For more information on adjusting permissions see Managing Permissions for Shared Folders.

From an elevated command prompt, run the following command:

Certutil -syncWithWU \\<server>\<share>

Substitute the actual server name for <server> and shared folder name for <share>. For example, if you run this command for a server named Server1 with a shared folder named CTL, you would run the command:

Certutil -syncWithWU \\Server1\CTL

Download the CTL files on a server that computers on a disconnected environment can access over the network by using a FILE path (for example, FILE://\\Server1\CTL) or an HTTP path (for example, HTTP://Server1/CTL).

Note

If the server that synchronizes the CTLs is not accessible from the computers in the disconnected environment, you must provide another method to transfer the information. For example, you can allow one of the domain member computers to connect to the server, then schedule another task on the domain member computer to pull the information into a shared folder on an internal web server. If there is absolutely no network connection, you may have to use a manual process to transfer the files, such as a removable storage device.

If you plan to use a web server, you should create a new virtual directory for the CTL files. The steps to create a virtual directory by using Internet Information Services (IIS) are nearly the same for all the supported operating systems discussed in this document. For more information, see Create a Virtual Directory (IIS7).

Be aware that certain system and application folders in Windows have special protection applied to them. For example, the inetpub folder requires special access permissions, which makes it difficult to create a shared folder for use with a scheduled task to transfer files. As an administrator, you are typically able to create a folder location at the root of a logical drive system to use for file transfers.

Redirect the Microsoft Automatic Update URL for a disconnected environment

If the computers in your network are configured in a domain environment and they are unable to use the automatic update mechanism or download CTLs, you can implement a GPO in AD DS to configure those computers to obtain the CTL updates from an alternate location.

To configure a custom administrative template for a GPO

On a domain controller, create a new administrative template. You can start this as a text file and then change the file name extension to .adm. The contents of the file should be as follows:

CLASS MACHINE
CATEGORY !!SystemCertificates
KEYNAME "Software\Microsoft\SystemCertificates\AuthRoot\AutoUpdate"
POLICY !!RootDirURL
EXPLAIN !!RootDirURL_help
PART !!RootDirURL EDITTEXT
VALUENAME "RootDirURL"
END PART
END POLICY
END CATEGORY
[strings]
RootDirURL="URL address to be used instead of default ctldl.windowsupdate.com"
RootDirURL_help="Enter a FILE or HTTP URL to use as the download location of the CTL files."
SystemCertificates="Windows AutoUpdate Settings"

If you save the file to the %windir%\inf folder, it will be easier to locate in the following steps.

Open the Group Policy Management Editor.

If you are using Windows Server 2008 R2 or Windows Server 2008, click Start, and then click Run.

If you are using Windows Server 2012 R2 or Windows Server 2012, press the Windows key plus the R key simultaneously.

Type GPMC.msc, and then press ENTER.

Warning

You can link a new GPO to the domain or to any organizational unit (OU). The GPO modifications implemented in this document alter the registry settings of the affected computers. You cannot undo these settings by deleting or unlinking the GPO. The settings can only be undone by reversing them in the GPO settings or by modifying the registry using another technique.

In the Group Policy Management console, expand the Forest object, expand the Domains object, and then expand the specific domain that contains the computer accounts that you want to change. If you have a specific OU that you want to modify, then navigate to that location. Click an existing GPO or right-click and then click Create a GPO in this domain, and Link it here to create a new GPO. Right-click the GPO you want to modify and then click Edit.

In the navigation pane, under Computer Configuration, expand Policies.

Click Windows AutoUpdate Settings, and in the details pane, double-click URL address to be used instead of default ctldl.windowsupdate.com.

Select Enabled. In the Options section, enter the URL to the file server or web server that contains the CTL files. For example, http://server1/CTL or file://\\server1\CTL. Click OK. Close the Group Policy Management Editor.

The policy is effective immediately, but the client computers must be restarted to receive the new settings, or you can type gpupdate /force from an elevated command prompt or from Windows PowerShell.

Important

The trusted and untrusted CTLs can be updated on a daily basis, so ensure that you keep the files synchronized by using a scheduled task or another method (such as a script that handles error conditions) to update the shared folder or web virtual directory. For additional details about creating a scheduled task, see Schedule a Task. If you plan to write a script to make daily updates, see the New Certutil Options and Potential errors with Certutil -SyncWithWU sections of this document. These sections provide more information about command options and the error conditions.

Redirect the Microsoft Automatic Update URL for untrusted CTLs only

Some organizations may want only the untrusted CTLs (not the trusted CTLs) to be automatically updated. To accomplish this, you can create two .adm templates to add to Group Policy.

Important

In a disconnected environment, you can use the following procedure with the previous procedure (redirect the Microsoft Automatic Update URL for trusted CTLs and untrusted CTLs). This procedure explains how to selectively disable the automatic update of trusted CTLs.

You can also use this procedure in a connected environment in isolation to selectively disable the automatic update of trusted CTLs.

To selectively redirect only untrusted CTLs

On a domain controller, create the first new administrative template by starting with a text file and then changing the file name extension to .adm. The contents of the file should be as follows:

In Add/Remove Templates, click Add. Use the Policy Templates dialog box to select the .adm templates that you previously saved. (You can hold the CTRL key, and click each file to select both.) Click Open, and then click Close.

The policy is effective immediately, but the client computers must be restarted to receive the new settings, or you can type gpupdate /force from an elevated command prompt or from Windows PowerShell.

Important

The trusted and untrusted CTLs can be updated on a daily basis, so ensure that you keep the files synchronized by using a scheduled task or another method to update the shared folder or virtual directory.

Use a subset of the trusted CTLs

This section describes how you can produce, review, and filter the trusted CTLs that you want computers in your organization to use. You must implement the GPOs described in the previous procedures to make use of this resolution. This resolution is available for disconnected and connected environments.

There are two procedures to complete to customize the list of trusted CTLs.

Create a subset of trusted certificates

Distribute the trusted certificates by using Group Policy

To create a subset of trusted certificates

From a computer that is connected to the Internet, open Windows PowerShell as an Administrator or open an elevated command prompt, and type the following command:

Certutil -generateSSTFromWU WURoots.sst

You can run the following command in Windows Explorer to open the WURoots.sst:

start explorer.exe wuroots.sst

Tip

You can also use Internet Explorer to navigate to the file and double-click it to open it. Depending on where you stored the file, you may also be able to open it by typing wuroots.sst.

In the navigation pane of Certificate Manager, expand the file path under Certificates -Current User until you see Certificates, and then click Certificates.

In the details pane, you can see the trusted certificates. Hold down the CTRL key and click each of the certificates that you want to allow. When you have finished selecting the certificates you want to allow, right-click one of the selected certificates, click All Tasks, and then click Export.

Important

You must select a minimum of two certificates to export the .sst file type. If you select only one certificate, the .sst file type is not available and the .cer file type is selected instead.

On the File to Export page, enter a file path and an appropriate name for the file, such as C:\AllowedCerts.sst, and then click Next. Click Finish. When you are notified that the export was successful, click OK.

Copy the .sst file that you created to a domain controller.

To distribute the list of trusted certificates by using Group Policy

On the domain controller that has the customized .sst file, open the Group Policy Management Editor.

In the Group Policy Management console, expand the Forest, Domains, and specific domain object that you want to modify. Right-click Default Domain Policy GPO, and then click Edit.

Enter the path and file name of the file that you copied to the domain controller, or use the Browse button to locate the file. Click Next.

Confirm that you want to place these certificates in the Trusted Root Certification Authorities certificate store by clicking Next. Click Finish. When you are notified that the certificates imported successfully, click OK.

Close the Group Policy Management Editor.

The policy is effective immediately, but the client computers must be restarted to receive the new settings, or you can type gpupdate /force from an elevated command prompt or from Windows PowerShell.

Registry settings modified

The settings described in this document configure the following registry keys on the client computers. These settings are not automatically removed if the GPO is unlinked or removed from the domain. These settings must be specifically reconfigured, if you want to change them.

If there is a change in the trusted root certificates, you will see: "Warning! Encountered the following no longer trusted roots: <folder path>\<thumbprint>.crt. Use "-f -f" options to force the delete of the above ".crt" files. Was "authrootstl.cab" updated? If yes, consider deferring the delete until all clients have been updated."